KR101695103B1 - Pulsed arc welding method - Google Patents

Abstract

The present invention provides a high-current pulse arc welding method capable of achieving suppression of tip abrasion while obtaining a reduction effect of a spatter. As a means for solving the problem, there is provided a method for performing pulse arc welding using a shielding gas, the pulse arc welding method comprising the steps of: setting a pulse peak current to 550 to 950 A, a pulse base current to 550 A or less, Pulse arc welding is performed with a difference of 200 to 600 A and a pulse frequency of 50 to 200 Hz.

Description

[0001] PULSED ARC WELDING METHOD [0002]

The present invention relates to a pulse arc welding method. More particularly, the present invention relates to a pulse arc welding method for performing welding at high current

In the field of welding applied to the field of transportation, construction equipment, etc., the fillet and the improvement are often welded by one layer or multi-layer using consumable electrode type gas-shielded arc welding. In such welding, high quality and high efficiency are always required.

As for high efficiency, a method of increasing the wire melting rate using a high current is used. However, since a large amount of spatter is generated in association with high currents, the appearance of the welded portion may be damaged, resulting in deterioration of the quality, and the labor of the step of removing the spatter is increased, and the production efficiency is lowered .

Conventionally, a solid wire is generally used as a consumable electrode. However, in the method of increasing the wire melting rate using the high current, when welding is performed at a high current of 400 A or more, a volume transfer called rotating transfer . As shown in Fig. 1A, in this transition, the joule heat generation becomes excessive in the wire protruding portion 1 from the feed tip to the arc generation point, and the softened and welded wire is stretched from its tip end portion, The distal end fused portion 2 is rotated along the arc 4 by an arc pressure or a plasma current generated during the arc. At this time, most of the displaced volume is scattered around, and the amount of spatter generated at this time becomes remarkable.

In addition to the rotation transition, for example, a globular transfer in which the volume 3 larger than the outer diameter of the wire projection 1 as shown in Fig. 1 (b) have. Further, there is a spray transfer in which the volume 3 smaller than the outer diameter of the wire projection 1 shown in Fig. 1C shifts. In the globulin transition (see Fig. 1B), large amounts of large spatter are generated. In the spray transfer (see FIG. 1C), the amount of spatters generated is reduced. Therefore, in order to reduce the amount of spatter generated, it is important to stabilize the transition of the volume, such as spray transfer.

On the other hand, as a gas shield arc welding method using a high current, for example, in Patent Documents 1 to 3, the following welding methods have been proposed.

In Patent Document 1, solid wires are used as electrode wires, and four kinds of wires each containing 40 to 70% by volume of argon, 25 to 60% by volume of helium, 3 to 10% by volume of carbon dioxide and 0.1 to 1% There has been proposed a welding method for obtaining a solid solution weight by using a mixed gas as a shielding gas.

In Patent Document 2, by employing a slag flux cored wire as an electrode wire and using carbon dioxide gas as a shielding gas and welding at a current density of 300 A / mm 2 or more, A welding method in which an effect is also obtained is proposed.

Patent Literature 3 discloses a technique of performing pulse arc welding using a flux cored wire in which a high peak current density, a pulse base current density, a smooth current density, A gas shielded arc welding method has been proposed.

Japanese Patent Application Laid-Open No. 1984-45084 Japanese Patent Application Laid-Open No. 1991-169485 Japanese Patent Application Laid-Open No. 2011-218437

The welding method disclosed in Patent Document 1 aims at stabilizing the spray transfer. However, there is a problem in that a large amount of spatter is generated because the spinning performance can not be improved until the rotation density is further improved when the current density is further increased.

Further, in the welding method disclosed in Patent Document 2, since the welding is carried out by using DC as the shielding gas, carbon dioxide gas is used as the shield gas, and therefore the mode of the volume is shifted to the globuler and a large amount of counter- have.

In Patent Document 3, it is possible to realize a remarkable spatter reduction while obtaining a solid solution weight by the welding method disclosed in the document, and as a result, it is possible to realize a high-efficiency welding which is higher than that of the prior art, And the effect of the improvement is described

However, high-current pulse arc welding has a large fluctuation of the arc length, and the arc tends to become unstable. From the fact that such an arc tends to become unstable, fine spatter or bad appearance of the bead tends to occur, resulting in a deterioration in quality. In addition, due to the high-current pulse arc welding, the periphery of the contact tip that energizes with a consumable electrode (hereinafter also referred to as " welding wire ") becomes hot and the contact surface of the tip becomes susceptible to wear exist. If the amount of abrasion of the contact surface of such a tip (hereinafter also referred to as " tip abrasion ") is increased, misalignment of the target position to be welded occurs, frequent exchanging of the tip occurs, and the work efficiency is lowered. From the above, it is required to stabilize the arc and to suppress the wear of the spatter and the contact tip when high-efficiency welding is performed at a high current.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a high-current pulse arc welding method capable of suppressing tip abrasion while obtaining a reduction effect of a spatter.

The present invention relates to a method for performing pulse arc welding using a shielding gas, wherein a pulse peak current is 550 to 950 A, a pulse base current is 550 A or less, a pulse peak current and a pulse base current And the pulse frequency is set to 50 to 200 Hz.

In this pulse arc welding method, the relationship between the pulse frequency and the feeding speed of the consumable electrode used in the pulse arc welding may satisfy the following expression (1).

[Equation 1]

1.50 (mm / 1 pulse) ≤ feeding speed (mm / sec) / pulse frequency (pulse number / sec) ≤ 9.00 (mm /

The slope of the external characteristic of the welding power source used for the pulse arc welding may be set in the range of -14.0 to -4.0 (V / 100A).

As the shielding gas, an Ar gas or an Ar-containing mixed gas containing 0 to 40% by volume of CO ₂ and 0 to 10% by volume of O ₂ and the remainder of Ar and impurities may be used.

According to the present invention, it is possible to provide a high-current pulse arc welding method capable of suppressing tip abrasion while obtaining a reduction effect of spatters.

FIG. 1A is a schematic view showing a rotation transition, which is a type of a transition form of volume in welding;
Fig. 1B is a schematic diagram showing a globuler transition, which is a type of a mode of transfer of a volume in welding;
Fig. 1C is a schematic view showing spray transfer, which is a type of transfer of the volume in welding;
Fig. 2 is a schematic view showing an example of a welding apparatus usable in the pulse arc welding method according to the embodiment of the present invention. Fig.
3 is a schematic diagram showing the name of a pulse waveform in the pulse arc welding method of the present embodiment,
Fig. 4 is a schematic diagram showing an example of the relationship between the pulse frequency and the amount of spatters in the conventional pulse MAG welding (NSWelding, technical information, welding Q & A, [online], [search on August 1, 2014] : http: /www.welding.nssmc.com/tech/qa/q026/qa026.html>),
FIG. 5 is a graph showing a constant voltage characteristic having an arc length self-controlling action (Exhibit: Japan Welding Association Electric Welding Machine Association "World of Arc Welding" published by Aichi Publishing Co., Ltd., April 15, p11-13),
Fig. 6 is a schematic view showing a configuration example of a welding torch for explaining a water-cooled welding torch used for the pulse arc welding method of the present embodiment,
Fig. 7A is a graph showing the results of Test Example No. 1 in Example. Fig. 1 shows the waveform of the time-arc voltage in Fig.
Fig. 7B is a graph showing the results of Test Example No. 3 in the example. Fig. The waveform of the time-arc voltage at 32,
Fig. 8A is a graph showing the results of Test Example No. 1 in Example. Fig. 1, a photograph of the bead appearance obtained in Example 1,
Fig. 8B is a graph showing the results of the test example No. 1 in the example. Fig. 32 is a photograph of the bead appearance taken from the viewpoint of the present invention.

Hereinafter, embodiments for carrying out the present invention will be described in detail. The present invention is not limited to the embodiments described below.

First, a welding apparatus usable in the pulse arc welding method according to the present invention will be described. Such a welding apparatus is not particularly limited as far as it is a welding apparatus for performing pulse arc welding, and a welding apparatus used for conventional gas shield arc welding can be used.

2, the welding apparatus 100 includes a consumable electrode 108 and a shield gas nozzle (not shown) for supplying a shield gas to the outer peripheral portion of the consumable electrode 108 at the front end A robot 104 for moving the welding torch 106 along the welding line of the welding material 107 and a welding torch 106 for welding the welding torch 106 to the welding torch 106 A pulse current is supplied to the consumable electrode 108 via the wire supply unit 101 to supply the consumable electrode 108 and a pulse arc is generated between the consumable electrode 108 and the material to be welded 107 And a power source control section 103 for controlling the pulse current of the welding power source section 102. The power source control section 103 controls the pulse current of the welding power source section 102, The welding apparatus 100 may further include a robot control unit 105 for controlling the robot operation for moving the welding torch 106. [ The power control unit 103 and the robot control unit 105 are provided with a CPU, a ROM, a RAM, an HDD, an input / output interface, and the like.

In the pulse arc welding method according to the embodiment of the present invention, the control of the pulse current in the control section of the welding power source, such as the welding power source section 102 in the welding apparatus 100 described above, is executed under predetermined conditions. Specifically, the range of the pulse current and the frequency of the pulse are defined as a specific range.

The pulse arc welding method of the present embodiment will be described below.

The pulse arc welding method of the present embodiment is a method of performing pulse arc welding using a shielding gas in which pulsed peak current is set to 550 to 950 A and pulse base current is set to 550 A or less At the same time, the difference between the pulse peak current and the pulse base current is set to 200 to 600 A, and the pulse frequency is set to 50 to 200 Hz.

The pulse waveform specified in the pulse arc welding method of the present embodiment is a repeated waveform of a rectangular or trapezoidal shape produced by using a pulse power source as shown in Fig. 3 (the case of a rectangle in Fig. 3 is exemplified) . In the present invention, the time of the upper peak portion of the rectangular or trapezoid is defined as the pulse peak period Tp and the time of the lower bottom portion is defined as the pulse base period Tb, Ip) and the pulse base current Ib, and the average current Ia is obtained by temporally averaging the time integral of the welding current. That is, in the case of a rectangular wave, Ia = (Ip 占 Tp + Ib 占 Tb) / (Tp + Tb). The number of pulses for one second (the number of times one wavelength is repeated) is set as a pulse frequency.

The pulse waveform may be, for example, a waveform of a triangular wave, a saw tooth wave, or a sinusoidal wave (sine wave) in addition to the waveform repeating the rectangular or trapezoidal shape described above.

As described above, in the pulse arc welding method, the volume generated in the pulse base period Tb and the pulse peak period Tp in which the current is low is deviated by the electromagnetic force of the pulse peak current Ip. Such a pulse arc welding method causes an increase in the spatter, deflection of the arc, and coarseness of the bead appearance if the pulse timing is inappropriate or the timing of the departure of the volume from the normal time. For example, when the pulse peak current Ip is low, the stiffness of the arc can not be obtained, and the arc may be deflected during the pulse peak period Tp. When the pulse base current Ib is high, the volume is scattered by the arc pressure of the pulse base current 1b, and the spatter may increase. Particularly, in the case of high current welding, it is difficult to obtain suitable pulse conditions since the rotation is likely to be performed, and the tip wear rate is also high.

The inventors of the present invention have studied the method of reducing the spatter and suppressing the tip abrasion in high-current pulse arc welding in view of the above-described pulse waveform and the phenomenon corresponding thereto. As a result, the inventors of the present invention have found the following explanations and found an appropriate range such as a pulse frequency, paying attention to the pulse frequency as a factor for obtaining an appropriate pulse condition.

As shown in Fig. 4, the pulse frequency of conventional pulse MAG welding generally employs a pulse frequency of 250 to 350 Hz because the amount of spatter tends to decrease as the pulse frequency increases.

However, in the case of performing welding with a high current, the arc length is more likely to fluctuate than in the prior art because a very high pulse peak current (Ip) and a low pulse base current (Ib) The fluctuation of the arc pressure applied to the molten portion becomes large. Therefore, the rotation transition is promoted, and arc deflection occurs. Further, by simply lowering the pulse peak current Ip and raising the pulse base current Ib, even if the average current is matched, the stiffness of the arc at the pulse peak current Ip is not required, and the arc is deflected, The transition period becomes irregular, and sometimes the timing of departing the volume is aimed at, so it can not be said that this is a convenient method. The stiffness of an arc is a phenomenon in which an arc has directivity due to the influence of a plasma current generated by an electron pressure difference acting on an arc, and the higher the current, the stronger the directivity.

In addition, the wear profile of the contact tip is such that the surface of the tip is dissolved by the heat of resistance of the contact point between the welding wire and the contact tip at the time of the pulse peak current Ip and is adhered to the welding wire at the time of the pulse base current Ib, Adhesion wear ". Therefore, since the contact tip tends to wear more as the temperature of the contact tip itself, the pulse peak current value, and the pulse frequency (the number of times of the pulse peak current Ip) become higher, The wear is particularly large.

On the other hand, if the high-current welding is performed at a frequency of 200 Hz or less, the pulse base period Tb can be guaranteed for a long time, so that abrupt fluctuation of the arc length can be suppressed and arc deflection can be suppressed. In addition, since the arc pressure applied to the volume is small in the pulse base period Tb, the movement of the volume increased in the pulse peak period Tp can be suppressed, and as a result, the rotation transition can be suppressed. Also, with respect to tip abrasion, the tip frequency is low and the cooling effect of the tip is expected in the pulse base period Tb, so that the tip wear is reduced.

Thus, in the pulse arc welding method of the present embodiment, the pulse frequency is defined as 200 Hz or less. Hereinafter, the specified range of the pulse frequency and the like will be described in more detail.

[Pulse frequency: 50 to 200 Hz]

If the pulse frequency exceeds 200 Hz, the arc length may fluctuate, which may result in an increase in spatter, a failure in bead appearance, and an increase in tip wear. On the other hand, if the pulse frequency is less than 50 Hz, the pulse peak period (Tp) becomes longer, and the increase of the spatter or the bead appearance may occur in such a period.

Therefore, in the pulse arc welding method of the present embodiment, the pulse frequency is defined in the range of 50 to 200 Hz.

Regarding the current range at such a pulse frequency, the pulse peak current Ip in the pulse peak period Tp is set to 550 to 950 A, and the pulse base current Ib in the pulse base period Tb is set to 550 A or less And the difference between the pulse peak current Ip and the pulse base current Ib is defined as 200 to 600 A. By performing the welding in such a current range, the arc of the pulse peak period Tp has rigidity and the arc deflection becomes difficult to occur. As a result, the electromagnetic force (pinch force) smoothly displaces the wire melting tip portion, and the stable volume transition can be made, so that the amount of spatter generated can be made extremely small. Further, an effect of improving the deposition amount by pulsing is also obtained.

[Pulse peak current: 550 to 950 A]

If the pulse peak current Ip is less than 550 A, not only the arc stiffness is insufficient, but also the effect of improving the deposition amount by pulsation is difficult to obtain. If the pulse peak current Ip exceeds 950 A, an arc current is applied to the wire fusing tip portion due to an excessive current, and the molten portion deforms to cause arc deflection. As a result, the arc becomes unstable, and the amount of generated spatters may increase. In addition, tip wear may increase. Therefore, in the pulse arc welding method of the present embodiment, the pulse peak current Ip is defined in the range of 550 to 950 A.

In the present embodiment, the pulse peak current Ip is preferably 600 A or more, from the viewpoint that improvement of the deposition amount can be expected. From the viewpoint of stabilizing the arc and controlling the amount of spatter generated, the pulse peak current Ip is preferably 900 A or less, and more preferably 850 A or less.

[Pulse base current: 550A or less]

If the pulse base current Ib exceeds 550 A, the arc pressure to the volume in the pulse base period Tb becomes excessive, so that the arc becomes unstable and the amount of generated spatter may increase. Therefore, in the pulse arc welding method of the present embodiment, the pulse base current Ib is defined to be 550 A or less.

In this embodiment, from the viewpoint of stabilizing the arc and suppressing the generation of spatter, the pulse base current Ib is preferably 500 A or less. The lower limit value of the pulse base current Ib is not particularly limited but the pulse base current Ib is preferably 50 A or less so that the difference between the pulse peak current Ip and the pulse base current Ib can be within the specified range, Or more, more preferably 100 A or more.

[Difference between pulse peak current and pulse base current: 200 ~ 600A]

When the difference between the pulse peak current Ip and the pulse base current Ib is less than 200A, the arc pressure to the volume in the pulse base period Tb becomes excessive, so that an unstable arc is generated, There is an increase. If the difference between the pulse peak current Ip and the pulse base current Ib exceeds 600 A, the arc pressure applied to the melting tip of the wire becomes large, and the molten part deforms, causing arc deflection. As a result, the arc becomes unstable, and the amount of generated spatters may increase.

In this embodiment, the difference between the pulse peak current Ip and the pulse base current Ib is preferably 220 A or more, from the viewpoint of arc stability. The difference between the pulse peak current Ip and the pulse base current Ib is preferably 550 A or less, more preferably 500 A or less, from the viewpoint of suppressing the amount of spatter generated.

(Feed speed / pulse frequency)

In addition, as described above, pulse arc welding may cause an increase in the amount of spatters to be generated and deterioration of the appearance of the beads if the displacement timing of the volume is deviated. Therefore, by controlling the feed rate (mm / sec) of the consumable electrode (welding wire) used for the pulse arc welding to a predetermined range in addition to the above-described prescribed welding conditions, control of volume transition, It is considered that the arc can be stabilized.

However, since the feed speed of the host is changed by the pulse frequency, the feeding speed (mm / second) divided by the pulse frequency (number of pulses per second) / pulse frequency (times / second) And specifies the range of the feed rate per wavelength.

If the relationship between the feeding speed (mm / sec) and the pulse frequency (number of pulses / sec) is 1.50 (mm / 1 pulse) or more, the arc length can be kept constant and more contributing to stabilization of the arc. On the other hand, if the relation between the feeding speed (mm / sec) and the pulse frequency (pulse number / sec) is 9.00 (mm / 1 pulse) or less, the arc length can be kept constant without being excessively short- It becomes possible to avoid the increase of the spatter

Therefore, in the pulse arc welding method of the present embodiment, it is preferable that the pulse frequency and the supply speed of the consumable electrode satisfy the following expression (1).

[Equation 1]

1.50 (mm / 1 pulse) ≤ feeding speed (mm / sec) / pulse frequency (pulse number / sec) ≤ 9.00 (mm /

The feeding speed / pulse frequency is preferably 1.70 (mm / 1 pulse) or more, more preferably 2.00 (mm / 1 pulse) or more from the viewpoint of stabilizing the arc. From the viewpoint of suppressing the amount of spatter generated, it is more preferable to set the feeding speed / pulse frequency to 8.80 (mm / 1 pulse) or less.

(External characteristic)

In the case of high-current pulse welding, the arc peak of the pulse peak current Ip makes the oscillation of the melting pores vigorous, and the arc length largely fluctuates. The slope of the external characteristic indicating the relationship between the load voltage and the load current of the welding power source of the arc welding machine is moderated to suppress the variation of the arc length so that the change of the current is made insensitive and the fluctuation of the arc length is suppressed more effectively . On the other hand, if the slope of the external characteristic is increased excessively, there is a fear that the self-controlling action of the arc length is lost. Therefore, in the pulse arc welding method of the present embodiment, it is preferable that the external characteristic (output characteristic) of the welding power source used for the welding be set to the constant voltage characteristic, and the inclination of the external characteristic is set to a predetermined range desirable.

In addition, self-regulating action of the arc length is, as shown in Figure 5, when the arc length is shortened to l _S from l _O, current is molten, the consumable electrode (welding wire), since the increase in I _S from the I _O It acts to hold the speed increases the arc length and the arc length is returned to its original length l of _O. Conversely when the arc length is lengthened by l _L from l _O, current is due to the decrease in I _L from the I _O, lowering the melting rate of the consumable electrode (welding wire), the arc length is also returned to the original length l _O of The same arc length is automatically controlled. This is because the slope of the external characteristic is more gradual. The following is a description of the range and the reason for the inclination of the external characteristic in the pulse arc welding method of the present embodiment.

When the slope of the external characteristic is -4.0 (V / 100A) or less, fluctuation of the arc length can be suppressed by controlling a large current change at the time of high-current pulse arc welding. Further, when the slope of the external characteristic is -14.0 (V / 100A) or more, the arc has a self-controlling action, and the variation of the arc length can be suppressed.

Therefore, in the pulse arc welding method of the present embodiment, the slope of the external characteristic is preferably set in the range of -14.0 to -4.0 (V / 100A).

The condition of the external characteristic has a particularly effective effect in the above-described pulse condition employed in the pulse arc welding method of the present embodiment. This is characterized by suppressing arc length variation due to current variation at the time of pulse as described above. However, in the case of the pulse frequency range adopted in the present embodiment, since the fluctuation of the melting paper becomes vigorous, it is desirable to make the slope of the external characteristic sharper than the conventional one.

(Shield gas)

The shield gas used in the pulse arc welding method of the present embodiment is not particularly limited, and Ar gas, carbon dioxide gas, and their mixture gas can be used. Also in pulsed arc welding using 100% CO ₂ as shield gas, the effect of reducing the spatter and suppressing the tip wear can be obtained by the above-described pulse conditions employed in the pulse arc welding method of the present embodiment. By using an Ar gas or an Ar-containing mixed gas as the shielding gas, the mode of volume transfer is spray-transferred, and the amount of spatter generated can be further reduced. Therefore, it is preferable to use an Ar gas or an Ar-containing mixed gas as the shielding gas.

When the content of CO ₂ in the shield gas mainly composed of Ar is 40% by volume or less, the arc pressure applied to the volume can be controlled and the volume transition is stabilized. In addition, O ₂ When the content is 10% by volume or less, occurrence of slag can be suppressed.

Therefore, as the shielding gas, Ar gas containing 0 to 40% by volume of CO ₂ (may be 0% by volume) and O ₂ : 0 to 10% by volume (may be 0% by volume) and the balance of Ar and impurities Or an Ar-containing mixed gas is more preferable.

(Welding material)

In the pulse arc welding method of the present embodiment, as described above, the welding material to be used is not particularly limited because the transition of the volume is stabilized even when high-frequency welding is performed by defining the pulse frequency and the current.

As a consumable electrode, it is preferable to use a flux cored wire since it is possible to further suppress the rotation transition during high current welding. Such a flux cored wire is constituted by an outer skin formed in a cylindrical shape and a flux filled in the inner tube. Therefore, since the flux cored wire is a non-uniform cross section in which the flux is present at the center, the temperature distribution of the wire cross section becomes discontinuous, and the phenomenon that the projected portion is softened and melted and the leading end is elongated as compared with the solid wire, can do.

The composition of the consumable electrode (welding wire) and the base material (welded material) is not particularly limited, since the behavior of the pulse arc welding method of the present embodiment hardly changes depending on the composition. The pulse arc welding method according to the present embodiment is advantageous in that the consumable electrode (when the above-described flux cored wire is used as the consumable electrode, the outer skin is used) And the base material (welded material) are preferably steel, more preferably carbon steel.

The welding torch used in the pulsed arc welding method of the present embodiment is not particularly limited, but a water-cooled welding torch (hereinafter also referred to as " water-cooled welding torch ") is used from the viewpoint of controlling the tip abrasion by the cooling effect Is preferably used. Fig. 6 is a schematic diagram showing a configuration example of a welding torch 106 generally used for arc welding to explain such a water-cooled welding torch. 6, the welding torch 106 is composed of a contact tip 6a as a power supply portion, a torch main body 6b, and a tip base portion 6c for detachably holding the contact tip 6a. In this embodiment, it is preferable to use a welding torch that is water cooled from the upper side of the torch main body 6b to the tip base portion 6c in this welding torch 106.

As described above, in the pulse arc welding method of the present embodiment, the pulse peak current, the pulse base current, the difference between the pulse peak current and the pulse base current, and the pulse frequency of the pulse arc welding are set to the above- do. By welding under such a pulse condition, in the high current pulse arc welding of the short electrode excellent in operability in the present embodiment, the volume transfer and the arc length are stabilized and the cooling effect of the tip is stabilized Therefore, the spatter can be reduced and the tip abrasion can be suppressed. As a result, it is possible to reduce the labor of the step of removing the spatter in the welding step, and the working efficiency of the welding step is further improved. In addition, since the wear of the contact tip can be controlled, the frequency of replacement of the tip can be reduced, thereby improving the work efficiency and lowering the cost.

Further, in the pulse arc welding method of the present embodiment, the volume transfer and the arc length are stabilized and the spatter can be further reduced by welding the feed rate / pulse frequency of the consumable electrode to a specific range, Can be further suppressed.

Further, in the pulse arc welding method of the present embodiment, the welding is performed by making the slope of the external characteristic of the welding power source in the range of -14.0 to -4.0 (V / 100A) The spatter can be further reduced, and it is possible to further suppress the wear of the contact tip.

By using an Ar gas or an Ar-containing mixed gas as the shield gas used in the pulse arc welding method of the present embodiment, the electron pinch effect applied to the tip of the consumable electrode (welding wire) becomes large, , The generation of the spatter can be further suppressed and welding can be performed. Further, in the pulse arc welding of the present embodiment, by using the water-cooled welding torch, the tip wear can be further suppressed by the cooling effect.

In addition, the pulse arc welding method of the present embodiment can be suitably applied to a fillet or an improvement in the field of a transport machine, a construction machine, etc., in the case of one-layer or multi-layer welding.

[Example]

Hereinafter, the effects of the present invention will be described in detail with reference to test examples.

First, in the pulse arc welding in the present test example, four kinds of flux cored wires (F1 to F4) having the composition and wire diameter shown in Table 1 below were used as consumable electrodes.

[Table 1]

Each condition of the arc welding was selected in the following range. In each of the test examples, pulse arc welding was performed using the shield gas and pulse parameters shown in Table 2 below.

· Pulse peak current: 450 ~ 1000A

· Pulse base current: 50 to 600A

· Pulse frequency: 30 ~ 310㎐

Average current: 400 to 600 A

· Feed speed of welding wire: 18 ~ 30m / min

· Arc voltage: Appropriate voltage (30 ~ 50V)

Shield gas: a mixed gas of a mixed gas of Ar and CO ₂ (CO ₂ content: 0 to 20% by volume) or Ar and O ₂ (O ₂ content: 0 to 10% by volume)

In addition, 48, as a conventional method, arc welding was performed at an average current of 550 A in constant voltage welding without using a pulse waveform.

As a base material (welded material), a steel sheet of JIS G3101 SS400 (size: 12 mm in thickness x 50 mm in width x 500 mm in length) was used. In addition, each irradiation was evaluated by downward welding of the bead-on-plate.

The conditions of the above-mentioned pulse arc welding were set to common welding conditions in the following evaluations.

(1) Evaluation of arc length variation (arc stability)

The variation of the arc length was judged from the naked eye using the light shielding surface and the current waveform. When the set peak current exceeds +50 A for 60 seconds and the base current is below -50 A, the count is counted. If the count at that time is 500 or more, the naked eye confirms that the arc is unstable , And it was judged that the fluctuation of the arc length was large and evaluated as " x " (defective). Further, when the number of counts was 250 or more and less than 500, it was judged that the suppression effect on the variation of the arc length was hardly seen, and evaluated as "? &Quot;. When the number of counts is less than 250, it is possible to confirm the state where the arc is stable by the naked eye, and it is judged that there is a good suppressing effect on the fluctuation of the arc length, and it is evaluated as " Good ".

For reference, FIG. The waveform of the time-arc voltage in Fig. 32 shows the waveform of the time-arc voltage in the case of FIG.

(2) Measurement and evaluation of the amount of spatter generated

The measurement of the generated spatters was carried out in such a manner that a box made of a steel plate was provided on both sides of the welded part in common to all of the examples and welding was carried out to collect the entire spatters generated in one minute from the inside of the box, The total mass of the collected spatters was measured to obtain the amount of spatters (g / min). When the amount of the spatter exceeds 1.50 g / min, it was judged to be worse than the spatter amount of the conventional constant-voltage welding and evaluated as " x " (defective). When the amount of spatter became 0.75 g / min or less which is half the amount of 1.50 g / min, it was judged that the effect of reducing the spatter was remarkably good, and evaluated as " Good ". When the amount of spatter was more than 0.75 g / min and not more than 1.50 g / min, it was judged that the effect of reducing spatter was "△" (possible).

(3) Bead appearance

The bead surface such as meander of the bead, humping, and weld defect of the undercut was judged by the naked eye. A case in which any one of these weld defects was identified was evaluated as " x " (defective), and a case where no weld defect was identified was evaluated as " O " (good).

For reference, FIG. Fig. 8B is a photograph showing the bead appearance obtained in Example 1, and Fig. 32 is a photograph showing a bead appearance obtained in the step of FIG.

(4) Tip wear

The tip abrasion was carried out by bead-on-plate welding with a large plate size of 650 mm in each side and 25 mm in thickness, and the difference between the tip hole area before welding and the tip hole area after welding for 30 minutes was determined as the wear area of the tip. The case where the wear area of the tip is 1.00 mm < 2 > or more is evaluated as " x " (defective) by judging that there is no restraining effect on the tip wear and the case where the wear area of the tip is less than 0.65 mm & , It was judged that there was an inhibiting effect on the tip abrasion which was equal to or more than the constant current welding of "? &Quot; (good). Further, when the tip abrasion area was 0.65 mm 2 or more and less than 1.00 mm 2, it was judged that the wear resistance effect was hardly observed and evaluated as "?" (Not possible).

The results of the above evaluation are shown in Table 2 and Table 3 together with the condition of the pulse arc welding.

The notations shown in Tables 2 and 3 respectively mean the following.

· F.rate: feed rate of welding wire

Ip: pulse peak current

Tp: pulse peak period

Ib: Pulse base current

Ip-Ib: Difference between pulse peak current and pulse base current

Ia: average current

Fp: Pulse frequency

[Table 2]

[Table 3]

Test No. 1 to 31, the pulse peak current, the pulse base current, the difference therebetween, and the pulse frequency are all within the range specified in the present invention, and the feeding speed / pulse frequency and the slope of the external characteristic are also in a range , It was suggested that the arc was stabilized, the generation of spatter was small, and the effect of suppressing the wear of the tip was suggested. In addition, 1 to 31, the bead appearance was good (see Fig. 8A).

On the other hand, 32 and No. 33, since the pulse frequency was too high, the arc became unstable, a large number of spatters were generated, and an inhibiting effect on tip abrasion was not recognized. In addition, 1 to 31, the bead appearance was also bad (see Fig. 8B).

Test No. 34 and No. 35, since the pulse frequency was too low, the arc became unstable and the bead meander occurred.

Test No. 36, since the pulse peak current was too high, the contact surface of the tip became easy to melt in the range of the pulse peak current, and the tip wear increased.

Test No. 37, the difference between the pulse peak current and the pulse base current became large, the arc became unstable, and the spatter and tip wear increased.

Test No. 38 to 47, since the pulse frequency was out of the range specified by the present invention, the arc became unstable and a lot of spatters were generated. Test No. 42 and No. 43 is a case in which a welding wire having a wire diameter of 1.2 mm is used. 42, the pulse frequency was too low. 43, since the pulse frequency was too high, the arc became unstable and the effect of reducing the spatter was not obtained. Test No. 44 to 47 use welding wires of different compositions, but since the pulse frequency was out of the range specified in the present invention, the arc was not stabilized and the effect of reducing the spatter was not obtained.

From the test results described above, by performing the welding within the range specified in the present invention for both the pulse peak current, the pulse base current, the difference thereof, and the pulse frequency in the pulse current of the pulse arc welding, The arc is stabilized, the spatter can be reduced, and the suppression effect on tip abrasion and a good bead appearance can be obtained.

1: wire protruding portion 2: tip melting portion
3: volume 4: arc
Tp: pulse peak period Tb: pulse base period
Ip: Pulse peak current Ib: Pulse base current

Claims (6)

A method of performing pulse arc welding using a shield gas,
In the pulse current of the pulse arc welding,
Pulse peak current is 550 ~ 950A,
Pulse base current is less than 550A,
The difference between the pulse peak current and the pulse base current is 200 to 600 A, and
Welding is performed at a pulse frequency of 50 to 200 Hz,
The relationship between the pulse frequency and the feed rate of the consumable electrode used in the pulse arc welding satisfies the following expression
Pulsed arc welding method.

[Equation 1]
1.50 (mm / 1 pulse) ≤ feeding speed (mm / sec) / pulse frequency (pulse number / sec) ≤ 9.00 (mm / delete The method according to claim 1,
The slope of the external characteristic of the welding power source used for the pulse arc welding is in the range of -14.0 to -4.0 (V / 100A)
Pulsed arc welding method. The method of claim 1, wherein
The shield gas is an Ar gas or an Ar-containing mixed gas composed of 0 to 40% by volume of CO ₂ and 0 to 10% by volume of O ₂ and the remainder consisting of Ar and impurities
Pulsed arc welding method. delete The method of claim 3,
The shield gas is an Ar gas or an Ar-containing mixed gas composed of 0 to 40% by volume of CO ₂ and 0 to 10% by volume of O ₂ and the remainder consisting of Ar and impurities
Pulsed arc welding method.

Images